The present invention relates to a new and improved blade for controlling the thickness of an ink film along a fountain roll in a printing press.
During the printing of newspapers or other publications, one column may require a far greater quantity of ink than an adjacent column. Thus, there may be relatively heavy or dark printing throughout one column of a newspaper and relatively large open or unprinted spaces in an adjacent column of the newspaper. Of course, a substantially greater amount of ink is required to print the dense column than the adjacent open column of the newspaper or other publication.
Printing presses have previously had ink metering assemblies with flexible blades which control the thickness of the ink film along an ink fountain roll. These ink metering assemblies may have a construction similar to that disclosed in U.S. Pat. Nos. 2,283,830; 4,242,958; 4,393,776; 4,495,864; and 4,453,467.
In order to vary the thickness of an ink film transferred to a fountain roll, keys or screws may be operated to flex a metering blade. Operation of an ink fountain key flexes a segment of the metering blade either toward or away from the roll to either decrease or increase the thickness of the film of ink applied to a zone on the roll. Optimization of the thickness of the ink film at various zones or locations along the roll requires that one segment of the blade be flexed relative to an adjacent segment without effecting the position of the adjacent segment.
To minimize the interaction between segments of a metering blade when the blade is flexed to adjust the position of one segment, it has been suggested that the metering blade have a slotted construction similar to that shown in U.S. Pat. No. 4,495,864. In order to prevent leakage of ink through the slots between adjacent segments and to eliminate stickiness between segments, it has been suggested that an elastic rubber-like material be used to seal or close the slots in the manner disclosed in U.S. Pat. No. 3,855,927. In this patent, the elastic rubber-like material is bonded to opposite side surfaces of the slots and to bottom surfaces of segments of the blade.
While the use of an elastic rubber-like seal material in a manner similar to that disclosed in U.S. Pat. No. 3,855,927 will prevent leakage of ink through the slots in the metering blade, this structure does not promote a precise adjustment of the individual segments of the blade relative to each other. This is because the segments are connected to each other by the elastic rubber-like material. Therefore, the position of one segment is changed relative to adjacent segments, forces are transmitted through the elastic rubber-like material between the two segments. Furthermore, continuous shear stresses acting on the elastic rubber-like material tends to cause it to rupture with a resulting requirement to replace the blade after a relatively short period of use. Deterioration of the elastic rubber-like material is promoted by solvents used in cleaning fluids for the rolls of the printing press.